Understanding reaction pathways in alkali metal-air batteries for high energy storage

Lead Research Organisation: University of Liverpool
Department Name: Chemistry


A major breakthrough in energy density is required to satisfy the energy storage needs of society in the long-term. Metal-oxygen batteries have theoretical energy densities up to 10 times that of the state-of-the-art Li-ion battery technology. The goal of this proposal is to enable the uptake of this technology by fully understanding the reduction and oxidation pathways taking place in alkali metal-oxygen batteries.

In situ electrochemical Raman is a surface sensitive technique which is able to follow at the molecular level these pathways in various Li+ containing non-aqueous solvents and also ionic liquids. What sets this work apart is that oxygen reduction reaction and oxygen evolution reaction will be investigated with Raman on multiple substrates, not just on Au, but also transition metal oxide catalysts, such as manganese dioxide (MnO2), noble metal catalysts, such as Pt and on practical electrode materials, such as carbon. The work will go further in the characterisation of oxygen reduction and oxygen evolution in the presence of other alkali metal cations (Na+ and K+) that also offer great gains in energy density as metal-O2 cells over Li-ion. These elements are much more abundant than lithium and therefore would offer a more sustainable energy storage solution for even beyond the long-term.

Planned Impact

The proposed research will have a considerable academic impact, nationally and internationally. It will also have significant potential impact beyond academia into the public and private sectors and society as a whole. Advances in battery research would impact on the battery industry and the enormous portable electronics industry (laptops, cameras, mobile phones and other hand-held devices).
A quarter of all manmade CO2 emissions arise from transportation, any breakthroughs in battery technology regarding significant increases in energy density (and therefore driving range) would allow future electric vehicles (EVs) to become a more attractive option for consumers. As a consequence our research will have a major impact on the automotive industry in the UK and worldwide. Moreover the UK will depend on more and more intermittent electricity supply from, for example, wind, wave and solar power. Energy storage will become crucial for the smoothing out of supply and demand and allowing for a less centralised grid. Improvements in battery performance will have significant impact on this nascent application and will allow greater adoption of green power and lower dependence on fossil fuel power stations, which will lower CO2 emissions in this sector (approximately 30% of total UK emissions).
Description We have characterised reaction mechanisms in metal-air batteries through our technique in situ Raman spectroscopy.

1. Using surface enhanced Raman spectroscopy (SERS) and shell isolated nanoparticles for enhanced Raman spectroscopy (SHINERS) we have established a strong dependency of the solvent donor number of the reaction pathways within the system. Our work has demonstrated that high donor number solvents favour the formation of NaO2 and low donor number solvents leading to surface Na2O2 films and the effect of different electrode substrates on the oxygen reduction reaction.
2. Established that shorter chain tetraalkylammonium cations: (1) enhance reversibility and rate of superoxide formation and oxidation and (2) for in situ SERS, have lower preference for adsorption, thus improving experimental detection of superoxide at the Au electrode interface
Exploitation Route Our results will allow other researchers to understand the effects on solvent choice reaction pathways and make evidence based decisions on what electrolytes to choose.
Sectors Energy